Etiology and treatment of community-acquired pneumonia in ambulatory children

Objectives. To determine the etiology of community-acquired pneumonia in am bulatory children and to compare responses to treatment with azithromycin, amoxicillin-clavulanate or erythromycin estolate, Methods, Ambulatory patients with pneumonia were identified at the Children 's Medical Center of Dallas, TX. Children age 6 months to 16 years with rad iographic and clinical evidence of pneumonia were enrolled and randomized t o receive either azithromycin suspension for 5 days or a 10-day course of a moxicillin-clavulanate for those <5 years or erythromycin estolate suspensi on for those greater than or equal to 5 years. Blood culture was obtained i n all patients and we obtained nasopharyngeal and pharyngeal swabs for cult ure and polymerase chain reaction (PCR) testing for Chlamydia pneumoniae an d Mycoplasma pneumoniae and nasopharyngeal swabs for viral direct fluoresce nt antibody and culture. Acute and convalescent serum specimens were tested for antibodies to C. pneumoniae, M. pneumoniae and Streptococcus pneumonia e, Patients were evaluated 10 to 37 days later when repeat specimens for se rology, PCR and culture were obtained. For comparative purposes healthy chi ldren attending the well-child clinic had nasopharyngeal and pharyngeal swa bs obtained for PCR and culture for C. pneumoniae and M, pneumoniae, Results. Between February, 1996, and December, 1997, we enrolled 174 patien ts, 168 of whom fulfilled protocol criteria for evaluation. There were 55% males and 63% were <5 years of age. All blood cultures were sterile and the re was no correlation between the white blood cell and differential counts and etiology of pneumonia, Etiologic agents were identified in 73 (43%) of 168 patients. Infection was attributed to IM, pneumoniae in 7% (12 of 168), C. pneumoniae in 6% (10 of 168), S, pneumoniae in 27% (35 of 129) and viru ses in 20% (31 of 157), None of the swab specimens from 75 healthy control children was positive for C. pneumoniae or M. pneumoniae, Clinical response to therapy was similes for the three antibiotic regimens evaluated, includ ing those with infection attributed to bacterial agents. Conclusion. Although a possible microbial etiology was identified in 43% of the evaluable patients, clinical findings and results of blood cultures, c hest radiographs and white blood cell and differential counts did not disti nguish patients with a defined etiology from those without a known cause fo r pneumonia, There were no differences in the clinical responses of patient s to the antimicrobial regimens studied.